Ozone production and loss rate measurements in the middle stratosphere

We present the first simultaneous measurements of HO x , NO x and Cl x radicals in the middle stratosphere obtained during a balloon flight at 34°N in September 1989, along with calculations from a photochemical model, to show that NO x catalytic cycles dominate loss of ozone (O 3 ) for altitudes between 24 and 38 km; the observed abundance of ClO is lower than that expected for altitudes above 30 km on the basis of models using recommended rates and cross sections, reducing the relative importance of the Cl x catalytic cycles for loss of O 3 ; and removal rates of O 3 derived from observed concentrations of rate limiting HO x , NO x , and Cl x radicals balance computed production rates for altitudes between 32 and 38 km, a region where ozone is expected to be regulated primarily by photochemical processes.